Operation check for molding machines



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Y W. STRAUSS OPERATION" CHECK FOR MOLDING MACHINES Original Filed Dec. 22, 1938 May 30, 1944.

W a; M y Mimi May 30, 1944. I v v w. STRAUSS 2,350,319

' OPERATION CHECK FOR HOLDING MACHINES Original Filed Dec. 22, 1938 2 Sheets-Sheet 2 INVENTOR LLIAM ST AUSS,

Patented May 30, 1944 OPERATION CHECK FOR MOLDING MACHINES William Strauss, Philadelphia. Pa., asslgnonto F. J. Stokes Machine Company, a corporation of Pennsylvania Original application December 22. 1938, Serial No. 247,215. Divided and this application June 24, 1941, Serial No. 399,523

6 Claims.

This invention relates to plastic-molding machines and, more particularly, to an automatic machine for the molding of finished articles from pulverulent compounds such as, for example,

Bakelite molding compound, a phenolic condensation product which hardens into the shape of the mold through the application of heat and pressure.

One purpose of this invention is to provide modifications and improvements of the automatic moldin machine described in the application of Victor I. Zelov and William Strauss, Serial #146,550, now Patent No. 2,242,189. In particular, the present invention relates to improve- This application is a division of my co-pending &

application, Serial No. 247,215, filed December 22, 1938. The claims in my earlier filed application are directed to the novel arrangement for unscrewing threaded molded articles from threaded,

mold parts, while the claims herein are directed to the improved operation check for controlling the continued operation of the molding press from one cycle to another.

Referring to the drawings:

Fig. 1 is a front elevation partly in section, showing so much of a machine suitable for my purpose as is necessary to embodying the improvements.

Fig. 2 is a sectional view taken on line 22 of Fig. 1 and showing the details of the operation check.

In the drawings there is shown a machine similar to one shown and described in the application of Victor I. Zelov and William Strauss, Serial #146,550, filed June 5, 1937, now Patent No. 2,242,189. This machine was selected and used only for the purpose of showing the principles of application and mode of operation of my invention. There is shown at IU (Figs. 1 and 2) a mold suitable for the production of screw caps from plastic material such as phenolics, ureas, cellulose acetate, methyl methacrylate, etc., of which there now is available a large variety, the mold I when open as shown in Fig. 2, being supplied by the feed device 11, with a sufiicient quantity of any one of these materials and then allowed to close as shown in Fig. 3, where the required pressure and heat is applied a sufiicient length of time to effect the molding and curing.

The mold is of a conventional type and com-- prises a die 3|, provided with a suitable cavity 30, mounted in a holder 32, resting on the lower platen 35 and a punch 28, attached to the upper platen 26. The upper platen 26 is provided with heating means 21 and a temperature control 25 and is mounted on the ram l I. The lower platen 35 is provided with heating means 34 and temperature control 36 and is attached to crosshead 44 of the pressure frame l3. Die holder 32 has a stem or spindle 38 extending down through lower platen 35 and connected to shaft 40 of motor I6 by the coupling 39.

In general, the machine consists of a frame 14, supporting a ram II with its operating mechanism connected to the reversing motor l8, which is controlled through suitable reversing switches from a controller so as to close or open the mold. On the frame I4 is also mounted a pressure frame l3 with its crosshead 44 and provisions 42 in the form of springs for producing the pressure required to be exerted on the molding compound while curing. Within frame 13 is mounted another frame l2, rigidly connected to the ram II, and therefore only acting and moving in conjunction with ram II. This frame l2 provides the means for operating the molding powder measuring and feeding device I! in timed relation with the movement of the ram H.

Any suitable master controller may be employed for the purpose of putting the machine through its paces of opening the mold, ejecting and discharging the molded piece, cleaning the mold, measuring and feeding the measured charge to the mold cavity, closing the mold, cleaning the face of the die around the punch and holdingthe mold closed under pressure the required length of time. With many pieces an additional step, that of breathing or degasing, must be introduced at a certain time in the curing period and this is taken care of by the proper setting of a set of dogs on the controller, so that the mold after a suitable time, will be opened for the required length of breathing time and then closed again for the curing period. The details of the controller and control circuits are not shown herein since they are conventional devices, but suitable devices for this purpose are disclosed in Zelov et al. Patent 2,242,189 and in my application Ser. No. 247,215. The extreme limit for the movement of the ram H, is controlled by a pair of limit switches, one of which acts to stop the motor when the ram has reached its topmost point of travel and the other acts to stop the motor on its downward stroke when the proper pressure is applied to the mold and the lower crosshead 44 has been depressed so as to dwell under the required tension from springs 42.

An operating check I9 is used for the purpose of controlling the continuity of operation. Every molded piece when discharged must pass through the operation check and .by means of interlocking switches keep the machine in continuous operation as long as pieces are discharged,- but in case of failure to discharge a molded piece, the

been discharged from the plate.

operation check functions to stop the machine before any damage can be done.

The operation check I 9 is preferably formed as a unitary device mounted on the opposite side of the die 3| from the air jet 64. The operation check consists of a main frame having two parallel side walls |9a and I92) and a back wall I9c secured to the back face of cross-head 44 by suitable screws or other fastening devices. Supported upon the frame I9a-l9b|9c is an inclined chute having a bottom wall l9d, a top wall I9e, and suitable side walls, the upper open end of the chute being arranged adjacent the die 3| and in position to receive the molded article as it is blown from the press by the air jet 64. The

lower end of the chute is positioned between the -side walls l9'a and I'Sb'of the frame, and is nragainst the lowerend of the chute when in its normal position I91". A second counter-weight I91 is ad'justably mounted upon a threaded screw 9 mounted upon the plate l9j' and extending at right angles thereto. The purpose of the second counter-weight l9i'is to urgethe plate |9f into contact with a fixed stop l9k (extending across 'thespace between walls 19a and l9b at the lower edge of these walls) and to hold the plate in contact with thisstop after the molded article has A mercury switch l9m is suitably mountedupon the tilting plate [9f and is normally open when the plate is in its normal position l9)" but is closed when the plate is moved-to its tripped position shown in Figure 2. This switch is-suitably'connected to "continue the operation of the main controller through another cycle each time a molded article is discharged'and operates'the plate to its tripped position. Since the plate- 19) will remain in its tripped position dueto the action of counterweight I91, it is necessary to provide means for resetting the plate to its normal position. Such 'means is'shown-in the form of a bell crank lever having two arms [9n and I90 mounted on opposite ends of ashaft l9pwhich is suitably jourpin I91 being mounted upon some part of the press which has relative upward movement with respect to the trap l9 an article has been discharged into the trap. For example, the pin I9r may be mounted on the main frame l4 so that when cross-head 44 is pressed down by the ram,

the" downward movement of the trap causes thebell crank to-rotate in a clockwise direction. In rotating from its normal position, the arm I90 engages a member 193 secured tothe plate l9 and causes the plate [9 to rotate in a counterclockwise direction into its normal position shown at I9 When cross-head returns to its normal position, the bell crank lever I9nI9o is returned to its normal position shown in Figure 2. As shown in the drawings, the upper wall 19c of the chute and preferably part of the side walls of the chute are formed of wire, netting whichwill deflect the discharged article downwardly along the chute but will allow the air blastfrom the avoiding undue air pressure on the upper face of plate l9f which might-result in false operation of the operation check.

The punch 28 is provided with threads on the outer surface thereof for forming internal threads on the screw cap to be molded in the die 3!, and in order to remove the cap from the punch 28, the die 3| is mounted for rotation by the motor l6 as explained above. The die should remain stationary while the article is being formed, but it is rotated while the press is being opened, and the rate of rotation is related to the rate of opening the press so that the threaded cap is unscrewed completely from the punch 28 before it is freed from the die 3|. For the purpose of. controlling the motor [6, I provide a sensitive switch controlled by operation of the press to start and stop the motor at the proper time.

The switching arrangement comprises the switch unit [5, mounted in anyconvenient way, for example, to frame l3, so that it will not be affected by the relative variation which exists with varying pressures on the mold. Any kind of quick acting make and break switch may be used, as for example 60, shown mounted within the housing 63, with terminal connections 58 and 59, so as to make or break the circuit connected tomotor l6. Because of the long movement required where the motor must remain stationary, I have provided'a lever 51, mounted within the housing 63 and urged by the spring 62" against the switch button 6|; Assuming that normally when the'mold is open we desire the rotation to take place, then a normally open switch might be used so that in the position shown, Fig.1, the circuit would be closed and the motor'rotating the mold member. In order to stop the motor at the desiredperiod' in the cycle, a switch finger is attachedto side rod 53 of frame lZT and placed at suchv apoint or distance from lever5! that it willbreak the circuit at the desired time and hold it open until returned to that same position. From previous descriptions it is understood that frame I2 is actuated or moved by the ram itself andtherefore switch finger 54 will move in unison with the punch member of the moldl' As no. two molds are exactly alike or no two molded pieces are exactly the same dimensions, the position of both the units l5 and switch nger 54 is made adjustable and can be set'to perform the unscrewing operation at the desired. time in the cycle. The amount of lost motion between the lever 51 and the contact point 6 of the switch can be varied to suit the need ofthe particular mold and molded piece being made.

ln molding, an article the cycle of operation of my machine might be as follows: With the mold open as shown in Figs. 1 and 2, and ram 1 I starting; on its down stroke to close the mold, a charge of material already measured out will be delivered to, the cavity 30 by the measuring and feedingjdevice l1 As soon asthemololingjcompound is delivered intothe mold cavity it com.- menses to heatup from the temperatureat which the die3l is kept and as-the punch 23 (also at the desired temperature); enters the mold cavity 39,-; it; compresses the molding compound within the'cavity against the. springs. 42,,reducing the powderrto a plastic:state,.gradually. forcing some ofi this plastic mass out over. the brim'of the cavity: until the. mold. is completely closed. The controller and timer. hold themoldclosed for the i jet 64 to pass through the wallv |9e,. thus predetermineditime:duringiwhich.time the molding compound is formed into the proper shape and cured sufiiciently so that it will retain its shape and resist distortion when ejected. At this point in the cycle the motor I8 is started through the action of controller and retracts ram. H and with it the ram frame 12 and punch 23.

As the frame [2 retracts, together with the ram and punch, it permits spring 62 to cause lever 51 to contact the switch button 6!, establishing a current supply to motor 15 which immediately will start to rotate the die holder 32 and the combined action of the retracting ram and the rotating die unscrews the molded piece. Through the action of the controller, the unscrewed molded piece is blown off the surface of the die 3| as soon as freed from punch 28, the air jets 64 being operated at the proper time by the controller, discharging the molded piece into operation check I9, and thus insuring continuity of operation. The molded piece having been delivered to the operation check IS, the ram will commence to close the mold again causing a measured charge of material to be delivered into the cavity 3%. Influenced by the movement of ram II and frame I2, the switch I5 is opened at the proper point and the rotation of the die stopped.

When the plate lily of the operation check is moved downwardly to the tripped position shown in Fig. 2, it remains in this position until the next downward stroke of the ram I! when the cross-head 44 is moved downwardly by the ram against the pressure of springs 42, and the downward movement of the operation check, which is carried by cross-head 44, causes operation of hell crank Min-I90 to reset the plate I97 in its normal position IN. The arrangement for biasing the plate iii) in its tripped or tilted position guards against the possibility of the plate returning to its horizontal position and opening switch l9m before the main controller has fully started on another cycle.

What I claim is:

l. A device for controlling the operation of a molding press wherein a molded article is discharged from the press at the end of each molding cycle, said device comprising a chute for receiving said discharged article, a tiltable barrier normally biased to a position across the path of travel of said article in said chute and being tiltable by said article in its passage through said chute, control means operated by the tilt ing of said barrier for controlling the operation of said press, means for biasing said barrier in I its tilted position independently of the discharged article, and means operated in timed relation with the operation of said press for returning said barrier to its normal position across the said chute.

2. An article controlled device comprising a chute for receiving said article, a tiltable barrier normally positioned across the path of travel of said article in said chute and being tiltable by said article in its passage through said chute, biasing means for retaining said barrier in its tilted position independently of said article, and means controlled by said barrier in its tilted position for returning said barrier to its normal position against the action of said biasing means.

3. A device for controlling the operation of .a molding press wherein a molded article is discharged from the press at the end of each molding cycle, said device comprising an inclined chute for receiving said discharged article, a pivotally mounted weighing plate positioned across the lower end of said inclined chute in a substantially horizontal position, and being tiltable under the weight of said article to an inclined position Where the article slides from said plate by gravity, means for gravity biasing said plate against the lower end of said chute when in its normal position and for gravity biasing said plate in the opposite direction against a fixed stop when in said inclined position, means controlled by the tilting of said plate from its horizontal position for continuingthe operation of said press, and means controlled in timed relation with the continued operation of said press for returning said plate to its normal position across the lower end of said chute.

4. A device for controlling the operation of a molding press wherein a molded article is discharged from the press at the end of each molding cycle, said device comprising an inclined chute for receiving said discharged article, a pivotally mounted plate positioned across the lower end of said inclined chute in a substantially horizontal position, and being tiltable under the weight of said article to a position where the article slides from said plate by gravity, a counterweight secured to said plate and being effective to hold said plate in its normal position across the lower end of said chute, and a second counter-weight secured to said plate and being effective in the tilted position of said plate to urge said plate against a fixed stop and to maintain said plate in tilted position after said article has been discharged from said plate, means con.- trolied by the tilting of said plate from its horizontal position for continuing the operation of press, and means controlled in timed relation with the continued operation of said press for returning said plate to its normal position across the lower end of said chute 5. A device for controlling the operation of a molding press wherein a molded article is discharged from the press at the end of each molding cycle, said device comprising a pivotally mounted weighing plate normally positioned in a substantially horizontal position for receiving said articles thereon, and being tiltable under the weight of said article to an inclined position Where the article slides from said plate by gravity, and gravity biasing means acting on said plate independently of said article for urging said plate in one direction when in its normal position and for urging said plate in the opposite direction against a fixed stop when in said inclined position.

6. A device for controlling the operation of a molding press wherein a molded article is discharged from the press at the end of each molding cycle, said device comprising a pivotally mounted weighing plate normally positioned in a substantially horizontal position for receiving said articles thereon, and biasing means for normally maintaining said plate in its horizontal position but permitting tilting of said plate under the weight of an article into a position where the article slides therefrom by gravity, said biasing means being effective to maintain said plate in its tilted position after the article has been discharged therefrom.

WILLIAM STRAUSS.

CERTIFICATE OF CORRECTION. Patent No. 2,550,519. May 50, 19M.

' WILLIAM STRAUSS.

of the above numbered patent requirlng correction as follows: Page 2, first column, 'line 57, before the word "an" insert -after-; and that the said Letters Patent should be read wid'l this correction therein that the same may onform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of August, A. D. 19%.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

